JP2019111446A - Radiographic system, image processing apparatus, control method for radiographic system, and control program for radiographic system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately correct a step component generated in a captured image even when the incident direction of radiation changes between a correction image and a captured image, a radiation image capturing system and an image processing apparatus. , A method for controlling a radiographic imaging system, and a control program for a radiographic imaging system. SOLUTION: A radiation imaging system 10 has a radiation image capturing device 141 for capturing a first radiation image, and a part thereof on a side farther from the radiation irradiation device 16 than the radiation imaging device 141 with respect to the incident direction of radiation. It is arranged in a superposed state and includes a radiographic image capturing apparatus 142 for capturing a second radiographic image. The control unit 30 is caused by the conversion layer step indicated by the conversion layer step component caused by the scintillator 98 of the radiation imaging apparatus 141 and the TFT glass substrate 90 of the radiation imaging apparatus 141 with respect to the second radiation image. A correction is performed to reduce each of the substrate steps indicated by the substrate step components generated in the process by different correction methods. [Selection diagram] FIG. 10

Description

  The present disclosure relates to a radiation imaging system, an image processing apparatus, a control method of the radiation imaging system, and a control program of the radiation imaging system.

  Conventionally, as a radiographic imaging apparatus for imaging a subject, for example, a radiographic imaging apparatus for performing radiographic imaging for the purpose of medical diagnosis is known. The radiation imaging apparatus detects radiation which is emitted from the radiation irradiation apparatus and transmitted through the subject and captures a radiation image. The radiation image capturing apparatus captures a radiation image by collecting and reading out charges generated according to the irradiated radiation.

  There are known techniques for performing imaging using a plurality of radiographic imaging devices, such as imaging a large object, for example, a long object. When a plurality of radiation imaging devices are arranged adjacent to each other, the end portions (parts) of the radiation imaging devices are overlapped and overlapped so that no defect of the radiation image occurs in the adjacent part. There is.

  At the overlapping portion of the radiographed radiation image, a level difference component occurs due to the level difference at the end of the radiation image capturing apparatus, and appears as a level difference artifact.

  Therefore, for example, in Patent Document 1, the luminance of a radiation image obtained by imaging a subject is corrected using a correction coefficient obtained from luminance data representing the contrast of an image obtained by performing X-ray imaging of the subject as a reference. Describes a description for correcting the reduction of the luminance of the overlapping area of the radiation imaging device.

  In addition, Patent Document 2 describes a technique for suppressing the luminance variation generated in the overlapping portion and facilitating the image processing after imaging by devising the overlapping method (overlapping area) of the radiation image capturing apparatus. ing.

JP, 2000-278607, A Unexamined-Japanese-Patent No. 2000-292546

  In the above-described technology, when the incident direction of the radiation incident on the radiation imaging apparatus changes, there may be a problem that the step component can not be properly corrected.

  The present disclosure has been made to solve the above-described problems, and even if the incident direction of radiation changes between the correction image and the photographed image, correction of the step component generated in the photographed image is performed. It is an object of the present invention to provide a radiation imaging system, an image processing apparatus, a control method of the radiation imaging system, and a control program of the radiation imaging system, which can be appropriately performed.

  In order to achieve the above object, a radiation imaging system according to the present disclosure generates a first conversion layer that converts radiation incident from a radiation irradiation device into light, and the light converted by the first conversion layer. A first radiation image capturing apparatus for capturing a first radiation image comprising a first substrate on which a plurality of first pixels for storing electric charge are formed, and a side farther from the radiation irradiating apparatus than the first radiation image capturing apparatus A plurality of second conversion layers arranged in a state in which a part of them is overlapped in the incident direction of the radiation, and a plurality of charges generated according to the light converted by the second conversion layer; A second radiation image capturing apparatus for capturing a second radiation image, a first radiation image and a second radiation image, and the second radiation image is obtained. , Of the first radiographic imaging device Each of the conversion layer step represented by the conversion layer step component resulting from the 1 conversion layer and the substrate step represented by the substrate step component resulting from the first substrate of the first radiation image capturing apparatus are reduced by different correction methods And a correction unit that performs correction.

  The correction unit of the radiation imaging system of the present disclosure may perform correction to reduce the conversion layer step by the first radiation image.

  The correction unit of the radiation imaging system of the present disclosure diverts the image of the region corresponding to the overlap region of the first radiation image for the overlap region where the image information is present in the first radiation image among the conversion layer step components. You may correct by doing.

  The correction unit of the radiation image capturing system according to the present disclosure derives a correction amount for smoothly connecting the first radiation image diverted and the conversion layer step in a region different from the overlap region among the conversion layer step components. The correction may be performed according to the derived correction amount.

  The correction unit of the radiation imaging system of the present disclosure may correct the conversion layer step after correcting the substrate step.

  Further, in the image processing device according to the present disclosure, a first conversion layer that converts radiation incident from the radiation irradiation device into light, and a plurality of first charges that accumulate charges generated according to the light converted by the first conversion layer. A first radiation image captured by a first radiation image capturing apparatus including a first substrate on which one pixel is formed, and a side farther from the radiation irradiating apparatus than the first radiation image capturing apparatus in a radiation incident direction A second conversion layer that converts radiation into light and a plurality of second pixels that store charges generated according to the light converted by the second conversion layer are formed in a state in which a part of them is overlapped. And a second radiation image obtained by the second radiation image capturing apparatus including the second substrate, and the second radiation image is generated due to the first conversion layer of the first radiation image capturing apparatus. Converted layer indicated by the converted layer step component Comprising the difference, and each of the substrate step indicated substrate stepped component generated due to the first substrate of the first radiation image capturing apparatus, a correction unit for correcting to reduce the different correction methods.

  Further, according to the control method of a radiation imaging system of the present disclosure, a first conversion layer that converts radiation incident from a radiation irradiation apparatus into light, and a charge generated according to the light converted by the first conversion layer are stored. A first radiation image capturing apparatus for capturing a first radiation image including a first substrate on which a plurality of first pixels are formed, and a side of the radiation further away from the radiation irradiation apparatus than the first radiation image capturing apparatus A second conversion layer for converting radiation into light, and a plurality of second ones for storing charges generated according to the light converted by the second conversion layer, which are disposed in a state of being partially overlapped with the incident direction. A control method of a radiation image capturing system comprising: a second radiation image capturing apparatus for capturing a second radiation image, comprising: a second substrate on which pixels are formed, the first radiation image and the second radiation image Step to get A conversion layer step indicated by a conversion layer step component generated due to the first conversion layer of the first radiation image capturing device with respect to the second radiation image, and a first substrate of the first radiation image capturing device Performing correction to reduce each of the substrate steps indicated by the resulting substrate step component by a different correction method.

  Further, a control program of a radiation imaging system of the present disclosure is for causing a computer to execute each step of the control method of the present disclosure.

  According to the present disclosure, even when the incident direction of radiation changes between the correction image and the captured image, an effect is obtained that correction of the step component generated in the captured image can be appropriately performed.

It is a schematic block diagram which shows schematic structure of an example of the radiographic imaging system which concerns on this Embodiment. It is a schematic block diagram which shows an example of the console for demonstrating the image processing function containing the various correction | amendment which concerns on this Embodiment. It is a block diagram showing an example of a structure of the radiographic imaging apparatus which concerns on this Embodiment. It is a line sectional view of an example of a pixel of a radiation detector concerning this embodiment. It is explanatory drawing for demonstrating the relationship between the radiation irradiation apparatus which concerns on this Embodiment, and an electronic cassette, and represents the state seen from the side. It is explanatory drawing for demonstrating the relationship between the radiation irradiation apparatus which concerns on this Embodiment, and an electronic cassette, and represents the radiographic imaging apparatus seen from the radiation irradiation apparatus side. It is explanatory drawing for demonstrating the relationship between the radiation irradiation apparatus which concerns on this Embodiment, and an electronic cassette, and represents the state which the radiographic imaging apparatus moved (moved) in FIG. 5B. It is explanatory drawing for demonstrating the radiographic image image | photographed by each radiographic imaging apparatus which concerns on this Embodiment. (1) shows a radiation image captured by the upper radiation imaging device. (2) shows a radiation image taken by the lower radiation imaging device. It is an explanatory view for explaining change of a position of a cinch step component and a glass step component concerning this embodiment. (1) shows the case where the angles of the radiation X incident on the imaging region are different. (2) shows the case where the radiation imaging apparatus has moved (moved). It is a flowchart showing an example of the flow of the image processing which corrects with respect to the imaging | photography image image | photographed with the upper radiation imaging device which concerns on this Embodiment. It is a flowchart showing an example of the flow of the image processing which corrects with respect to the imaging | photography image image | photographed with the lower side radiation imaging device concerning this Embodiment. It is a schematic diagram for demonstrating an example of the flow of the image processing which corrects with respect to the imaging | photography image image | photographed with the lower side radiation imaging device which concerns on this Embodiment. FIG. 6 is a schematic configuration diagram for describing an example in which a plurality of electronic cassettes are arranged adjacent to each other. It is a schematic block diagram for demonstrating another example which arrange | positioned several electronic cassettes adjacently.

  Hereinafter, an example of the present embodiment will be described with reference to the drawings.

  First, the schematic configuration of the entire radiation imaging system including the radiation image processing apparatus of the present embodiment will be described. FIG. 1 is a schematic diagram showing the overall configuration of an example of a radiation imaging system according to the present embodiment. In the radiation imaging system 10 of the present embodiment, the electronic cassette 12 includes a plurality of radiation imaging devices 14.

  The radiation imaging system 10 according to the present embodiment is configured such that, based on an instruction (imaging menu) input from an external system such as RIS (Radiology Information System) via the console 20, for example, It has a function to take a radiation image by the operation of a technician or the like.

  In addition, the radiation image capturing system 10 according to the present embodiment displays a radiation image captured by the electronic cassette 12 on a display unit (see FIG. 2) of the console 20 or a radiation image reading apparatus (not shown). And radiologists, etc. have the function of reading radiographs. Note that the radiation image reading apparatus (not shown) is an apparatus having a function for a reader to read a radiograph taken, and is not particularly limited. However, so-called reading viewers, displays, portable terminals, and tablets A terminal etc. are mentioned.

  The radiation imaging system 10 of the present embodiment includes an electronic cassette 12, a radiation irradiation apparatus 16, and a console 20.

  The radiation irradiating device 16 has a function of irradiating the object X with a radiation X from a tube (not shown) as a radiation irradiating source based on the control of the console 20. The radiation irradiating apparatus 16 is an operation input unit for the user to manually set the irradiation conditions of the radiation X such as the tube voltage, the tube current, and the irradiation time directly to the radiation irradiating apparatus 16, or the irradiation set. You may provide the display part for displaying conditions etc. In addition, the radiation irradiating apparatus 16 transmits, to the console 20, information indicating that the setting has been made manually, the setting value by the setting manually, and the current status (standby state, preparation state, during exposure, end of exposure, etc.). In the following description, the position of the tube is assumed to be equal to the position of the radiation irradiating device 16.

The radiation X transmitted through the subject 18 is irradiated to the electronic cassette 12. The radiation imaging device 14 of the electronic cassette 12 generates an electric charge corresponding to the dose of the radiation X transmitted through the subject 18, and generates and outputs image information indicating a radiation image based on the generated electric charge amount. Have. In the present embodiment, generating and outputting image information is referred to as photographing. The electronic cassette 12 of the present embodiment includes a plurality of radiation imaging devices 14 (14 _{1 to} 14 ₃ ) in a housing 13 (details will be described later).

  In the present embodiment, image information indicating a radiation image output by the electronic cassette 12 is input to the console 20. The console 20 according to the present embodiment has a function of controlling the electronic cassette 12 and the radiation irradiating apparatus 16 using a photographing menu and various information obtained from an external system or the like via a wireless communication LAN (Local Area Network) or the like. have. Further, the console 20 of the present embodiment has a function of transmitting and receiving various information to and from the electronic cassette 12. The console 20 also has a function of outputting a radiation image acquired from the electronic cassette 12 to a PACS (Picture Archiving and Communication System) 22. The radiation image taken by the electronic cassette 12 is managed by the PACS 22.

  The console 20 of the present embodiment is a server computer. FIG. 2 shows an example of a schematic configuration diagram of the console 20 for explaining an image processing function including various corrections. The console 20 includes a control unit 30, a display unit drive unit 32, a display unit 34, an operation input detection unit 36, an operation input unit 38, an I / O (Input Output) unit 40, an I / F (Interface) unit 42, and an I / O (Interface) unit 42. An F unit 44 and a storage unit 50 are provided.

  The control unit 30 has a function of controlling the entire operation of the console 20, and includes a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and a hard disk drive (HDD). ing. The CPU has a function of controlling the overall operation of the console 20, and various programs including an image processing program used by the CPU are stored in advance in the ROM. The RAM has a function of temporarily storing various data, and the HDD has a function of storing and holding various data. Further, the control unit 30 functions as a correction image acquisition unit and a photographed image acquisition unit. The control unit 30 also has a function of performing image processing including various corrections on various images.

  The display drive unit 32 has a function of controlling display of various information on the display unit 34. The display unit 34 according to the present embodiment has a function of displaying an imaging menu, a captured radiation image, and the like. The operation input detection unit 36 has a function of detecting an operation state or processing operation on the operation input unit 38. The operation input unit 38 is used by the user to input a processing operation related to radiographing of a radiation image and image processing of the radiographed radiograph. The operation input unit 38 may have a form of a keyboard as an example, or may have a form of a touch panel integrated with the display unit 34. Further, the operation input unit 38 may be configured to include a camera, and may have a form of inputting various instructions by causing the camera to recognize a gesture of the user.

  The I / O unit 40 and the I / F unit 42 have a function of transmitting and receiving various information to and from the PACS 22 and RIS by wireless communication or the like. The I / F unit 44 also has a function of transmitting and receiving various types of information to and from the radiation imaging device 14 and the radiation irradiation device 16.

  The storage unit 50 has a function of storing a photographed image, a gain calibration image, and the like (details will be described later).

  The control unit 30, the display unit drive unit 32, the operation input detection unit 36, the I / O unit 40, and the storage unit 50 are mutually connected so as to be able to exchange information etc. via the bus 46 such as a system bus or control bus. It is done.

Next, a schematic configuration of the electronic cassette 12 of the present embodiment will be described. The electronic cassette 12 includes a plurality of radiation imaging devices 14. In this embodiment, as a specific example, as shown in FIG. 1, there will be described a case where the electronic cassette 12 is provided with three radiographic imaging device 14 (14 1 _{to 14 3),} radiation The number of image capturing devices 14 is not limited to the present embodiment. The radiation imaging devices 14 ₁ , 14 ₂ , and 14 ₃ are referred to as a radiation imaging device 14 when not distinguished from one another or collectively referred to.

  Three radiation imaging devices 14 are housed in the housing 13. As shown in FIG. 1, in the present embodiment, the radiographic imaging device 14 has an imaging region (imaging surface) facing the subject 18 and is disposed adjacent to the object 18. In the electronic cassette 12 according to the present embodiment, as shown in FIG. 1, the end (a part) of the radiation imaging device 14 is disposed overlapping with the adjacent radiation imaging device 14 (details will be described later) .

  By arranging a plurality of (three) radiographic imaging devices 14 in this manner, the entire electronic cassette 12 has a long imaging region.

  In FIG. 3, the block diagram showing an example of a structure of the radiographic imaging apparatus 14 which concerns on this Embodiment is shown. In the present embodiment, a case will be described where the present invention is applied to an indirect conversion type radiation image capturing apparatus 14 in which radiation such as X-rays is once converted into light and the converted light is converted into electric charge. In addition, in FIG. 3, the scintillator 98 (refer FIG. 4) which converts a radiation into light is abbreviate | omitted.

  The radiation image capturing apparatus 14 of the present embodiment includes a radiation detector 26, a scan signal control circuit 104, a signal detection circuit 105, a control unit 106, and a power supply 110.

  The radiation detector 26 receives light to generate charge, and generates a sensor unit 103 for storing the generated charge, and a TFT (Thin Film Transistor) switch 74 which is a switch element for reading out the charge accumulated in the sensor unit 103. And a pixel 100 configured to include. In the present embodiment, the light converted by the scintillator 98 (see FIG. 4) is irradiated, whereby the sensor unit 103 generates a charge.

  A plurality of pixels 100 are arranged in a matrix in one direction (gate wiring direction in FIG. 3) and in a cross direction (signal wiring direction in FIG. 3) with respect to the gate wiring direction. Although FIG. 3 shows the arrangement of the pixels 100 in a simplified manner, for example, 1024 × 1024 pixels 100 are arranged in the gate wiring direction and the signal wiring direction.

  Further, in the radiation detector 26, a plurality of gate wirings 101 for turning on / off the TFT switch 74 and a plurality of signal wirings 73 for reading out the charges accumulated in the sensor section 103 cross each other. Is provided. In the present embodiment, one signal wiring 73 is provided in each pixel column in one direction, and one gate wiring 101 is provided in each pixel column in the cross direction. For example, in the case where 1024 pixels × 1024 pixels 100 are arranged in the gate wiring direction and the signal wiring direction, 1024 signal wirings 73 and 1024 gate wirings 101 are provided.

  Furthermore, the radiation detector 26 is provided with a common electrode wire 95 in parallel with each signal wire 73. One end and the other end of the common electrode wiring 95 are connected in parallel, and one end is connected to a power supply 110 that supplies a predetermined bias voltage. The sensor unit 103 is connected to the common electrode wiring 95, and a bias voltage is applied via the common electrode wiring 95.

  A control signal for switching each TFT switch 74 flows through the gate wiring 101. When the control signal flows to each gate wiring 101 in this manner, each TFT switch 74 is switched.

  According to the switching state of the TFT switch 74 of each pixel 100, an electrical signal corresponding to the charge stored in each pixel 100 flows through the signal wiring 73. More specifically, an electrical signal corresponding to the amount of charge accumulated in each of the signal wirings 73 flows when one of the TFT switches 74 of the pixel 100 connected to the signal wiring 73 is turned on.

  Each signal wiring 73 is connected to a signal detection circuit 105 that detects the electric signal flowing out to each signal wiring 73. Further, a scan signal control circuit 104 that outputs a control signal for turning on / off the TFT switch 74 to each gate wiring 101 is connected to each gate wiring 101. Although FIG. 3 shows the signal detection circuit 105 and the scan signal control circuit 104 in a simplified form, for example, a plurality of the signal detection circuit 105 and the scan signal control circuit 104 are provided and a predetermined number of (for example, 256) lines are provided. The signal wiring 73 or the gate wiring 101 is connected every time. For example, in the case where 1024 signal wirings 73 and 1024 gate wirings 101 are provided, four scan signal control circuits 104 are provided, 256 gate wirings 101 are connected, and four signal detection circuits 105 are provided. The signal lines 73 are connected one by one.

  The signal detection circuit 105 incorporates, for each of the signal lines 73, an amplification circuit (not shown) for amplifying the input electric signal. In the signal detection circuit 105, the electric signal input from each signal wiring 73 is amplified by an amplification circuit, and converted into a digital signal by an ADC (analog-digital converter).

  The signal detection circuit 105 and the scan signal control circuit 104 perform predetermined processing such as noise removal on the digital signal converted by the signal detection circuit 105, and indicate the signal detection timing to the signal detection circuit 105. A control unit 106 that outputs a control signal and outputs a control signal indicating the timing of the output of the scan signal to the scan signal control circuit 104 is connected.

  The control unit 106 according to the present embodiment is a microcomputer, and includes a non-volatile storage unit (not shown) including a CPU (central processing unit), a ROM and a RAM, a flash memory, and the like. The control unit 106 performs control for capturing a radiation image by causing the CPU to execute the program stored in the ROM.

  A cross-sectional view of the pixel 100 is shown in FIG. As shown in FIG. 4, the pixel 100 (radiation detector 26) includes a TFT glass substrate 90 and a scintillator 98. As shown in FIG. 4, in the TFT glass substrate 90, a gate wiring 101 (see FIG. 3) and a gate electrode 72 are formed on an insulating substrate 71 made of non-alkali glass or the like. The gate wiring 101 and the gate electrode 72 are connected. The wiring layer in which the gate wiring 101 and the gate electrode 72 are formed (hereinafter also referred to as “first signal wiring layer”) is formed using a laminated film mainly made of Al or Cu, or Al or Cu. However, it is not limited to these.

  An insulating film 85 is formed on one surface of the first signal wiring layer, and a portion located on the gate electrode 72 acts as a gate insulating film in the TFT switch 74. The insulating film 85 is made of, for example, SiNx or the like, and is formed by, for example, CVD (Chemical Vapor Deposition) film formation.

  A semiconductor active layer 78 is formed in an island shape on the gate electrode 72 on the insulating film 85. The semiconductor active layer 78 is a channel portion of the TFT switch 74, and is made of, for example, an amorphous silicon film.

  A source electrode 79 and a drain electrode 83 are formed on the upper layer thereof. In the wiring layer in which the source electrode 79 and the drain electrode 83 are formed, the signal wiring 73 is formed together with the source electrode 79 and the drain electrode 83. The source electrode 79 is connected to the signal wiring 73. The wiring layer in which the source electrode 79, the drain electrode 83, and the signal wiring 73 are formed (hereinafter also referred to as "second signal wiring layer") is made of a laminated film mainly made of Al or Cu, or Al or Cu. Although formed, it is not limited to these. An impurity-doped semiconductor layer (not shown) made of impurity-doped amorphous silicon or the like is formed between the source electrode 79 and the drain electrode 83 and the semiconductor active layer 78. The TFT switch 74 for switching is comprised by these. The source electrode 79 and the drain electrode 83 are reversed depending on the polarity of the charge collected and accumulated by the lower electrode 81 described later.

  In order to protect the TFT switch 74 and the signal wiring 73, a TFT protective film layer 88 is provided on substantially the entire surface (substantially the entire area) of the region on the substrate 71 where the second signal wiring layer is covered. It is formed. The TFT protective film layer 88 is made of, for example, SiNx or the like, and is formed by, for example, CVD film formation.

  A coated interlayer insulating film 82 is formed on the TFT protective film layer 88. The interlayer insulating film 82 is a photosensitive organic material having a low dielectric constant (relative dielectric constant εr = 2 to 4) (for example, a positive photosensitive acrylic resin: a base polymer comprising a copolymer of methacrylic acid and glycidyl methacrylate) And a material in which a naphthoquinone diazide type positive photosensitive agent is mixed, etc.) to a thickness of 1 to 4 .mu.m.

  In the TFT glass substrate 90 according to the present embodiment, the interlayer insulating film 82 suppresses the capacitance between metals disposed in the upper and lower layers of the interlayer insulating film 82 to a low level. In addition, generally, such a material also has a function as a planarizing film, and also has an effect of planarizing the lower step. In the TFT glass substrate 90 according to the present embodiment, the contact hole 87 is formed at a position facing the interlayer insulating film 82 and the drain electrode 83 of the TFT protective film layer 88.

  The lower electrode 81 of the sensor unit 103 is formed on the interlayer insulating film 82 so as to cover the pixel region while filling the contact hole 87, and the lower electrode 81 is connected to the drain electrode 83 of the TFT switch 74. There is. If the lower electrode 81 is conductive when the semiconductor layer 91 described later is as thick as about 1 μm, there is almost no restriction on the material if it has conductivity. Therefore, there is no problem if it is formed using a conductive metal such as an Al-based material and ITO (Indium Tin Oxide: indium tin oxide).

  On the other hand, when the film thickness of the semiconductor layer 91 is thin (about 0.2 to 0.5 μm), light absorption is not sufficient in the semiconductor layer 91, and thus, to prevent an increase in leakage current due to light irradiation to the TFT switch 74, It is preferable to use an alloy mainly composed of a light shielding metal or a laminated film.

  A semiconductor layer 91 functioning as a photodiode is formed on the lower electrode 81. In this embodiment, a photodiode having a PIN structure in which an n + layer, an i layer, and ap + layer (n + amorphous silicon, amorphous silicon, p + amorphous silicon) are stacked is employed as the semiconductor layer 91. The semiconductor layer 91 is formed by sequentially stacking an n + layer 91 A, an i layer 91 B, and a p + layer 91 C from the lower layer. The i layer 91 B is irradiated with light to generate charges (a pair of free electrons and free holes). The n + layer 91A and the p + layer 91C function as a contact layer, and electrically connect the lower electrode 81 and an upper electrode 92 described later and the i layer 91B.

  Upper electrodes 92 are individually formed on the respective semiconductor layers 91. For the upper electrode 92, for example, a material with high light transmittance such as ITO or IZO (Indium Zinc Oxide: zinc indium oxide) is used. In the TFT glass substrate 90 according to the present embodiment, the sensor unit 103 is configured to include the upper electrode 92, the semiconductor layer 91, and the lower electrode 81.

  On the interlayer insulating film 82, the semiconductor layer 91, and the upper electrode 92, there is an opening 97A at a part corresponding to the upper electrode 92, and a coating type interlayer insulating film 93 is formed to cover each semiconductor layer 91. There is.

  On the interlayer insulating film 93, the common electrode wiring 95 is formed of Al or Cu, or an alloy or laminated film mainly composed of Al or Cu. A contact pad 97 is formed in the vicinity of the opening 97 A, and the common electrode wiring 95 is electrically connected to the upper electrode 92 through the opening 97 A of the interlayer insulating film 93.

In the TFT glass substrate 90 thus formed, a protective film is formed of an insulating material having a low light absorbability, if necessary, and radiation conversion is performed on the surface using an adhesive resin having a low light absorbency. A scintillator 98 which is a layer is attached. Alternatively, the scintillator 98 is formed by vacuum evaporation. As the scintillator 98, a scintillator that generates fluorescence having a relatively wide wavelength range that can generate light in an absorbable wavelength range is desirable. Such scintillator _{98, CsI: Na, CaWO 4} , YTaO 4: Nb, BaFX: Eu (X is Br or Cl), or, LaOBr: Tm, and there is a GOS or the like. Specifically, when imaging using X-ray as radiation X, one containing cesium iodide (CsI) is preferable, and CsI: Tl (thallium is added with an emission spectrum at 400 nm to 700 nm at the time of X-ray irradiation It is particularly preferable to use cesium iodide) or CsI: Na. The emission peak wavelength of CsI: Tl in the visible light range is 565 nm. When a scintillator containing CsI is used as the scintillator 98, it is preferable to use one formed as a strip-like columnar crystal structure by vacuum evaporation.

  As shown in FIG. 4, the radiation detector 26 is irradiated with radiation X from the side on which the semiconductor layer 91 is formed, and reads a radiation image by the TFT glass substrate 90 provided on the back side of the radiation X incident surface. In the case of the so-called back side reading method (PSS (Penetration Side Sampling) method), light is emitted more strongly on the upper surface side of the scintillator 98 provided on the semiconductor layer 91 in the figure. On the other hand, a so-called surface reading method (ISS (Irradiation Side Sampling) method), in which radiation X is irradiated from the TFT glass substrate 90 side and a radiation image is read by the TFT glass substrate 90 provided on the surface side of the radiation X incident surface In this case, the radiation X transmitted through the TFT glass substrate 90 is incident on the scintillator 98, and the TFT glass substrate 90 side of the scintillator 98 emits light more strongly. In the sensor section 103 of each pixel 100 provided on the TFT glass substrate 90, an electric charge is generated by the light generated by the scintillator 98. For this reason, since the radiation position of the scintillator 98 with respect to the TFT glass substrate 90 is closer when the radiation detector 26 is in the front side reading mode than in the back side reading method, the resolution of the radiation image obtained by imaging is Is high.

  The radiation detector 26 is not limited to those shown in FIGS. 3 and 4, and various modifications are possible. For example, in the case of the back side reading method, since the possibility of the radiation X reaching is low, it is replaced with the above-mentioned one with another imaging element such as a complementary metal-oxide semiconductor (CMOS) image sensor having low resistance to the radiation X. You may combine with TFT. In addition, it may be replaced with a CCD (Charge-Coupled Device) image sensor which transfers charges while shifting charges by a shift pulse corresponding to a gate signal of the TFT.

  For example, a flexible substrate may be used. As a flexible substrate, it is preferable to apply what used the ultra-thin plate glass by the float method developed in recent years as a base material, in order to improve the transmittance of radiation. As for the ultra-thin glass applicable to this case, for example, “Asahi Glass Co., Ltd.” succeeded in developing the world's thinnest 0.1-mm-thick ultra-thin glass by the float method ”, [online], [2011] [August 20 search] is disclosed on the Internet <URL: http://www.agc.com/news/2011/051.pdf>.

  Next, the radiation imaging device 14 in the electronic cassette 12 of the present embodiment will be described. In the following, as a specific example, the case of using the ISS type radiation imaging device 14 will be described. 5A to 5C show explanatory views for explaining the relationship between the radiation irradiation device 16 and the electronic cassette 12. FIG. 5A shows the state seen from the side, and FIG. 5B shows the radiation imaging device 14 seen from the radiation irradiation device 16 side. FIG. 5C shows a state in which the radiographic imaging device 14 has moved (moved) in FIG. 5B. In addition, description of the housing | casing 13 is abbreviate | omitted in FIG. 5A-FIG. 5C.

  As a specific example, as shown in FIG. 5B, the radiation image capturing apparatus 14 of the present embodiment is provided with the scan signal control circuit 104 on one side on the long side of the imaging area of the radiation detector 26. (In FIG. 5A, the scan signal control circuit 104 is not shown). Further, as shown in FIG. 5B, the signal detection circuit 105 is provided on one side intersecting the side on which the scan signal control circuit 104 of the radiation detector 26 is provided. The signal detection circuit 105 is stacked on the radiation detector 26 as shown in FIG. 5A. When imaging is performed, the electronic cassette 12 is disposed such that the side (imaging region) on which the radiation detector 26 of each radiation imaging device 14 is provided faces the radiation irradiation device 16 (see FIG. 5A). .

  In the radiation image capturing apparatus 14 of the present embodiment, as a specific example, as shown in FIG. 5A, the TFT glass substrate 90 is larger than the scintillator 98. More specifically, the area facing the radiation irradiation device 16 is larger for the TFT glass substrate 90 than for the scintillator 98. In the present embodiment, the range (size) of the imaging region is determined in accordance with the area of the scintillator 98 facing the radiation irradiation device 16.

  In the electronic cassette 12 according to the present embodiment, as shown in FIG. 5A, due to the following reasons (1) to (3), etc., it is adjacent to the end (part) of the imaging region of the radiographic imaging device 14 The end portions of the radiographic imaging device 14 are arranged to overlap each other. Specifically, the imaging regions overlap so as to overlap with the incident direction of the radiation X.

(1) When the interval between the imaging regions of each of the radiation imaging devices 14 is increased, there may be a portion which is not imaged on the imaging region of the subject 18. In this case, the radiation image capturing apparatus 14 _{1-14 3} long which connect the captured radiographic image in each of the radiographic images (the electronic cassette 12 overall radiographic image), so that the defects.

  (2) When mass producing the radiation image capturing apparatus 14 (the radiation detector 26), adjacent radiation detectors 26 are brought into close contact with each other due to manufacturing variations of the radiation image capturing apparatus 14 (the radiation detector 26). It becomes difficult to arrange without gaps.

  Furthermore, the radiation imaging device 14 (radiation detector 26) may expand due to temperature. In such a case, if the adjacent radiation detectors 26 are closely attached to each other without any gap, there is a concern that the TFT glass substrate 90 may be damaged.

  (3) In addition, when the temperatures of the radiographic imaging devices 14 are different, the expansion rate is different. Therefore, in the electronic cassette 12 of the present embodiment, the radiation imaging devices 14 are fixed to the housing 13 while the radiation imaging devices 14 are arranged without being fixed. Because they are not fixed to each other, the radiation imaging device 14 (radiation detector 26) moves (moves, see FIG. 5C).

  In addition, the range (size) of the imaging region of the overlapping portion overlapped corresponds to the oblique insertion of the radiation X irradiated from the radiation irradiating device 16, the movement of the radiation image photographing device 14 (movement, see FIG. 5C), etc. It should be determined.

As shown in FIG. 5A, in the radiation imaging system 10 of the present embodiment, the position of the radiation irradiating device 16 is movable in the direction along the longitudinal direction of the electronic cassette 12. Therefore, the position of the radiation irradiating device 16 differs depending on the imaging region of the subject 18 (see FIG. 1) to be imaged, the type of imaging, etc., and the relative position to the long imaging region of the electronic cassette 12 is displaced. . Therefore, according to the position of the radiation irradiation apparatus 16, in each radiation imaging device 14, the angle of the incident radiation X differs. Specifically, in FIG. 5A, the overlapping portion of the radiation image capturing apparatus 14 ₁ and the radiographic imaging apparatus 14 _2, the radiation X emitted from the position B is incident so as to be substantially perpendicular to the imaging region, position The radiation X emitted from A is obliquely incident on the imaging region. Further, as shown in FIG. 5C, when the radiographic imaging device 14 moves (moves), the imaging region of the overlapping portion changes.

  In consideration of various cases such as these, in the electronic cassette 12 of the present embodiment, the range of the imaging area of the overlapping portion is determined with a margin so that the imaging areas do not overlap.

In the electronic cassette 12 of the present embodiment, as shown in FIG. 5A, as a specific example, the radiation image capturing apparatus 14 ₁ and 14 ₃ are viewed from above (radiation irradiation device 16 side upper, the radiation irradiation device 16 side close), radiographic imaging apparatus 14 ₂ is lower when viewed from below (radiation irradiation device 16 side, an end portion farther) and a so-called terrace-shaped radiation irradiation device 16 is superimposed.

  If the signal detection circuit 105 is provided so as to be sandwiched between the radiation imaging devices 14, the signal detection circuit 105 may be reflected in the radiation image, as in the present embodiment. Preferably, the signal detection circuit 105 is overlapped so as not to be pinched.

Next, imaging of a radiation image by the electronic cassette 12 will be described. In the electronic cassette 12 of the present embodiment, the radiation image is taken by the all radiation image capturing apparatus 14 by one irradiation (one shot) of the radiation X. FIG. 6 is an explanatory view for explaining a radiation image taken by each radiation imaging device 14. 6 (1) shows a radiation image captured by the radiation imaging apparatus 14 _1. 6 (2) shows a radiation image captured by the radiation imaging apparatus 14 _2.

In the radiation imaging devices 14 (14 ₁ , 14 ₃ ) disposed on the upper side, the captured radiation images are radiations captured using the single radiation imaging device 14 as shown in FIG. 6 (1). It will be similar to the image.

On the other hand, the radiation image capturing apparatus 14 ₂ disposed on the lower side, as described above, the overlapping portion of the upper of the radiographic image capturing apparatus 14 (14 1, _{14 3),} a step is formed. Due to the step, as shown in FIG. 6 (2), the shadow of the overlapping part of the radiation imaging device 14 (14 ₁ , 14 ₃ ) on the upper side is reflected in the captured radiation image, and the step component Will occur. In the radiation image capturing apparatus 14 ₂ of the present embodiment, since the position of the end portion of the TFT glass substrate 90 and the scintillator 98 of the radiation detector 26 are different, a step component which is due to the step by TFT glass substrate 90, and scintillator 98 Two types of level difference components of level difference components resulting from level differences are generated. In the following, a component corresponding to an image of a region of a portion other than two types of step components in a radiation image is referred to as a normal component.

  In the present embodiment, the step component caused by the step due to the scintillator 98 is referred to as a cinch step component, and the step component due to the step due to the TFT glass substrate 90 is referred to as a glass step component. Further, when the cinch step component and the glass step component are not distinguished, they are collectively referred to as a step component. Furthermore, an image representing the boundary between the cinch step component and the glass step component is called a cinch step, and an image representing the boundary between the glass step component and the normal component is called a glass step. Further, when the cinch step and the glass step are not distinguished from one another, they are collectively referred to as a step.

Since the shadows of the radiation imaging devices 14 (14 ₁ , 14 ₃ ) on the upper side are captured, the density of the corresponding area (image) is different between the cinch step component, the glass step component, and the ordinary component.

FIG. 7 is an explanatory view for explaining changes in positions of the cinch step component and the glass step component. Figure 7 shows an end region including the cinch stepped component and glass stepped component due to the end portion of the radiation image capturing apparatus 14 ₁ in the captured radiographic images by the radiographic imaging apparatus 14 _2. FIG. 7A shows the case where the angles of the radiation X incident on the imaging region are different. When the angle of the radiation X incident on the imaging region is different, the cinch step component and the glass step component are different in position according to the incident angle, and the positions of the cinch step and the glass step are different. As shown in FIG. 7A, the cinch step and the glass step when radiation X is applied from position A (see FIG. 5A) and radiation X when applied from position B (see FIG. 5A) The position differs between the cinch step and the glass step.

  FIG. 7 (2) shows the case where the radiographic imaging device 14 has moved (moved) as shown in FIG. 5C. When the radiographic imaging device 14 moves (moves), the cinch step component and the glass step component differ in angle according to the movement (movement), and the cinch step and the glass step become the cinch step and the glass step before the move. It becomes non-parallel to. As shown in FIG. 7 (2), the cinch step and the glass step when photographed in the state of FIG. 5B (before movement) and the cinch step and the glass when photographed in the state of FIG. 5C (after movement) The steps are not parallel to each other.

Thus, in the radiographic image taken by the radiographic imaging apparatus 14 ₂ of the present embodiment, in accordance with the position of the radiation irradiating apparatus 16 and the radiographic imaging apparatus 14 of the motion (the incident angle of the radiation) (mobile), The positions of the cinch step component and the glass step component change. That is, positional deviation of the cinch step component and the glass step component occurs.

In the radiation image captured by the radiation imaging apparatus 14 _2, according to the position of the irradiation apparatus 16 (incident angle of the radiation), the position of the cinch step and the glass step is substantially translated in the longitudinal direction. Further, in the radiographic image taken by the radiographic imaging apparatus 14 _2, the movement of the radiation image capturing apparatus 14 according to the (mobile), the angle of the cinch step and the glass step changes.

  Next, correction of the radiation image taken by each of the radiation imaging devices 14 of the electronic cassette 12 in the radiation imaging system 10 of the present embodiment will be described. Various corrections are performed on the radiation image captured by the radiation imaging device 14 by image processing.

  In the radiographic imaging system 10 of the present embodiment, the radiographic image captured by each radiographic imaging device 14 of the electronic cassette 12 is output from the control unit 106 of each radiographic imaging device 14 to the console 20. The console 20 functions as each functional unit such as a correction unit that performs various corrections and image processing including correction of positional deviation of the step component on the radiation image input from each radiation imaging device 14. The function as the correction unit is not limited to that of the control unit 30 of the console 20, and may have other functional units of the console 20 or may have the electronic cassette 12 or the radiographic imaging device 14 . Also, the functional units that perform the correction may be different depending on the type of correction.

  The type of correction performed by the console 20 differs depending on the arrangement (upper and lower sides) of the radiographic imaging device 14.

  In the console 20 of the present embodiment, the correspondence between information such as an ID indicating the radiation imaging device 14 and the arrangement (upper side, lower side) is stored in advance in the storage unit 50. Further, the radiation image input to the console 20 is temporarily stored in the storage unit 50. The radiation imaging device 14 associates the ID indicating the device with the radiation image and outputs the radiation image to the console 20. By referring to the correspondence stored in the storage unit 50, the console 20 can recognize which of the upper and lower radiation image capturing apparatuses 14 the radiation image is captured.

  The method of recognizing whether the radiation image capturing apparatus 14 that has captured the radiation image is disposed on the upper side or the lower side is not limited to the present embodiment. For example, information indicating whether each radiation imaging apparatus 14 is the upper side or the lower side may be added to the radiation image and output to the console 20.

When the console 20 according to the present embodiment performs correction (step correction, details will be described later) on a radiation image (hereinafter referred to as a captured image) obtained by capturing the subject 18 with the lower radiation imaging device 14 (14 ₂ ) The corrected captured image of the upper radiation imaging device 14 (14 ₁ , 14 ₃ ) is referred to. Therefore, first, the correction on the upper side of the radiographic imaging apparatus 14 ₍₁₄ 1, 14 ₃₎ in the images picked up.

The correction of the captured image captured by the upper radiation imaging device 14 (14 ₁ , 14 ₃ ) will be described. Figure 8 is a flowchart showing an example of the upper radiographic imaging device 14 (14 1, _{14 3)} image processing flow for correcting for image captured by the. The console 20 according to the present embodiment performs three types of correction, offset correction, gain correction, and defect correction, on a captured image captured by the radiation image capturing apparatus 14 (14 ₁ , 14 ₃ ) on the upper side.

In step S100, the control unit 30 of the console 20 acquires a captured image of the radiation image capturing apparatus 14 on the upper side, which has been temporarily stored from the storage unit 50. Specifically, the control unit 30 according to the present embodiment acquires a photographed image of one of the radiographic imaging devices 14 ₁ and 14 ₃ . In the following, as a specific example of a captured image captured by the radiation imaging device 14, a captured image (radiographic image) obtained by capturing the subject 18 with the radiation X irradiated from the position B (see FIG. 5A) will be described. Do.

In the next step S102, the control unit 30 acquires, from the storage unit 50, gain calibration images (described in detail later) corresponding to the acquired captured images (radiographic image capturing apparatuses 14 ₁ and 14 ₃ ).

  In the next step S104, the control unit 30 performs offset correction of the captured image. The offset correction is to correct the variation of the offset (zero point) photographed in the state where the radiation X is not irradiated. The offset component includes the dark current of each pixel 100 of the radiation detector 26 of the radiation image capturing apparatus 14, the offset of the amplifier of the amplification circuit built in the signal detection circuit 105, and the like, which change according to the temperature.

  In the next step S106, the control unit 30 performs the gain correction and the defect correction of the photographed image, and then ends the present process.

  Gain correction (gain calibration) is to correct variation in sensitivity of each pixel 100 on the entire imaging region of the radiation detector 26. In gain correction, based on a radiation image (hereinafter referred to as a gain calibration image) captured by irradiating the imaging region with radiation X in a state in which no shielding object exists in the imaging region or in a state in which a reference object is present. , Correct the captured image. The gain component includes the intensity distribution of the radiation X irradiated from the radiation irradiating device 16, the dispersion of the sensitivity of each pixel 100 of the radiation detector 26, and the dispersion of the gain of the amplifier of the amplification circuit built in the signal detection circuit 105. is there.

  The console 20 according to the present embodiment acquires the gain calibration image of each radiographic image capturing device 14 captured by irradiating the radiation X from the position A (see FIG. 5A) in a state where the shielding object is not present in the imaging region. The information is stored in advance in the storage unit 50 in association with information such as an ID indicating the radiation imaging device 14. The control unit 30 corrects the variation in sensitivity of each pixel 100 of the radiation detector 26 based on the gain calibration image stored in the storage unit 50 to perform gain correction of the captured image.

Although the irradiation position of the radiation X is different between the gain calibration image and the photographed image, in the upper radiation imaging devices 14 (14 ₁ and 14 ₃ ), since no step component is generated, the gain correction is appropriately performed. be able to.

  The defect correction is to correct the pixel value of the pixel 100 in which the defect occurs. In defect correction, the pixel value of a defective pixel is interpolated based on the pixel values of surrounding pixels.

  The photographed image subjected to the offset correction, the gain correction, and the defect correction in this manner is stored in the storage unit 50.

Next, the control unit 30 of the console 20 corrects the captured image captured by the lower radiation imaging device 14 (14 ₂ ).

The correction of the captured image captured by the lower radiation imaging device 14 (14 ₂ ) will be described. FIG. 9 is a flow chart showing an example of the flow of image processing for correcting a captured image captured by the lower radiation imaging device 14 (14 ₂ ).

In the console 20 according to the present embodiment, in addition to the above-described offset correction, gain correction, and defect correction, four types of step correction are performed on the captured image captured by the lower radiation imaging device 14 (14 ₂ ). Make corrections for

In the following, to avoid the explanation to become complicated, the case of performing the step correction due to the radiation image capturing apparatus 14 _1. Also, as a specific example, the position (radiation incident angle of radiation) of the radiation irradiating device 16 differs between the time of capturing the gain calibration image (position A) and the time of capturing the captured image (position B). A case where the radiographic imaging device 14 moves (moves) will be described.

FIG. 10 is a schematic view for explaining an example of the flow of image processing for performing correction on a captured image captured by the lower radiation image capturing apparatus 14 (14 ₂ ).

  The control unit 30 of the console 20 detects the positions of the cinch step component and the glass step component from the gain calibration image in advance before performing the image processing shown in FIG. The method of detecting the position of the cinch step component and the glass step component from the gain calibration image is not particularly limited.

  As a specific example of detecting a cinch difference, the control unit 30 according to the present embodiment detects the positions of the cinch difference component and the glass difference component on the gain calibration image after the noise removal process is performed. There is. As processing for removing noise, for example, main direction median filter processing is performed as high frequency removal processing. The main direction is a direction intersecting the sub direction of the electronic cassette 12. Further, the auxiliary direction is the direction in which the radiation irradiation apparatus 16 moves, and in the present embodiment, the longitudinal direction of the electronic cassette 12. Also, for example, moving average filtering may be applied, and other high frequency removal filters may be applied.

  As a method of detecting the position of the cinch step component and the glass step component with respect to the gain calibration image after the noise removal processing, for example, by detecting a straight line (image representing a straight line) from the gain calibration image The cinch step and the glass step may be detected, and the positions of the cinch step component and the glass step component may be detected based on the detected cinch step and the glass step. The method of detecting the straight line is not particularly limited, and a general method may be used, for example, Hough transform (Hough transform) or the like may be used.

In step S200 of the image processing, as in step S100 described above, the control unit 30 of the console 20 acquires a captured image of the lower radiation image capturing apparatus 14 temporarily stored from the storage unit 50. Specifically, the control unit 30 of this embodiment obtains the photographed image of the radiographic imaging device 14 _2.

In the next step S202, the control unit 30 acquires, from the storage unit 50, a gain calibration image corresponding to the acquired captured image (radiographic imaging device 14 ₂ ), as in step S102 described above.

  In the console 20 according to the present embodiment, in order to easily detect the position of the step from the photographed image, offset correction and defect correction are performed before detection of the position of the step. Therefore, in the next step S204, the control unit 30 performs offset correction of the captured image, as in step S104 described above.

  In the next step S206, gain correction and defect correction of the photographed image are performed. Note that, in the gain correction in this step, the gain correction of the photographed image which has been subjected to the offset correction in step S204 is performed on the basis of the gain calibration image (a gain calibration image without any correction) acquired in step S202.

  The method of gain correction and defect correction is not particularly limited. Note that, since the captured image and the gain calibration image that are acquired include the step component, the QL value (pixel value) of the step component portion is lower than that of the normal component portion. Therefore, it is preferable to perform gain correction and defect correction in consideration of the decrease in the QL value of the step component portion.

  Although a specific example of the gain correction performed by the control unit 30 of the present embodiment will be described, the method of the gain correction is not particularly limited. It is not preferable that the radiation field be narrowed on the radiation detector 26 because the gain correction is to correct the variation in sensitivity for each pixel. In addition, it is not desirable that the attenuation of the radiation X is excessive due to the influence of the heel effect because the SID (Source Image Distance) is too short. Therefore, in the gain correction performed by the control unit 30 according to the present embodiment, the pixel value is too large or too small to detect the irradiation field stop or to detect the attenuation of the radiation X due to the excessive heel effect. If it does, it is judged as an error. In the step component portion, since the QL value greatly decreases, the error determination is performed in consideration of this. In the step component portion where the radiographic imaging device 14 overlaps, the pixel value is greatly reduced. Therefore, the ratio of the pixel value between the overlapping region and the non-overlapping region is determined in advance as the setting value, and the error is determined. By multiplying the threshold value of the upper limit and the lower limit by the ratio of the setting value, it is possible to determine the abnormality of the pixel value by removing the influence of the radiation absorption in the overlapping region. After the abnormality of the pixel value is determined in this manner, the gain correction of the photographed image which has been subjected to the offset correction is performed based on the gain calibration image.

  As described above, the position (radiation incident angle of radiation) of the radiation irradiating device 16 at the time of imaging differs between the gain calibration image and the captured image. In addition, the radiographic imaging device 14 is moving (moved). Therefore, as described above, the position of the step component generated in the gain calibration image is different from the position of the step component generated in the captured image. Since the position of the step component is different between the gain calibration image and the photographed image, when gain correction is performed, the step component of the gain calibration image and the step component of the photographed image and two step components are generated in the image after correction. . The level difference component of the present embodiment includes the cinch level difference component and the glass level difference component, so that four level differences occur in the image after gain correction (see FIGS. 10 and 7 (2)).

  Also, although a specific example of defect correction performed by the control unit 30 of the present embodiment will be described, the method of correcting defects is not particularly limited. The control unit 30 according to the present embodiment performs statistical processing on the surroundings of the captured image that has been offset-corrected by processing with the median filter in the main direction and the sub direction, the moving average filter, the high frequency filter, and the like. Defect correction is performed by an algorithm that determines the difference between the captured image and the captured image before processing as a threshold. The threshold value is compared for each pixel 100 to determine whether or not it is a defective pixel based on the threshold value. The threshold value is the ratio of the pixel value of the result of performing the statistical processing of the surrounding with the median filter to the pixel value of the normal component, and the threshold value multiplied by the ratio is used as the threshold value of the overlapping portion.

  In the next step S208, the control unit 30 multiplies the photographed image by the inverse coefficient. In the present embodiment, inverse gain correction is performed as a specific example of the inverse coefficient. As described above, four steps are generated in the captured image to be subjected to the inverse gain correction in this step.

  The control unit 30 according to the present embodiment performs the inverse gain correction based on the gain calibration image for the inverse gain correction acquired in advance. As the gain calibration image for inverse gain correction, a gain calibration image in which noise such as high frequency noise is removed by high frequency removal processing is acquired in advance. The method of removing noise is not particularly limited. For example, median filtering with a mask size capable of removing point defects and line defects may be applied to the main direction and sub direction, or moving average filtering may be applied. Alternatively, other high frequency removal filters may be applied.

After that, in the control unit 30 according to the present embodiment, as a specific example, a step component (a step component caused by radiation X absorption by the scintillator 98 and radiation X by the TFT glass substrate 90 with respect to a gain calibration image from which noise is removed). Step out the absorption-induced step component). In practice, the position of the step component is not exactly known, but a region in which the step component is generated can be obtained in design or by experiment etc. Therefore, by trimming the region including all the obtained regions, Trim the step component. In the Geinkyaribu image shown in FIG. 10 shows a step component caused by the radiation image capturing apparatus 14 _1, in fact, has also caused the stepped component by radiographic imaging apparatus 14 ₃ to Geinkyaribu image . Therefore, the control unit 30 cuts out both step components. That is, the control unit 30 trims the step component from both ends of the gain calibration image.

  The control unit 30 adjusts the QL value to generate a gain calibration image for inverse gain correction so that an image (corresponding to a normal component) between the trimmed both step components is smoothly connected with both step components. . The control unit 30 performs inverse gain correction by multiplying a gain calibration image for inverse gain correction acquired in advance by the defect-corrected photographed image in the process of step S206.

  The position of the step component of the gain calibration image used for the inverse gain correction is different from that of the photographed image, but is the same as the gain calibration image used for the gain correction in step S206. Therefore, by performing the inverse gain correction, the step component caused by the gain calibration image is removed, and the four steps generated in the captured image return to the two steps.

  Further, by performing the inverse gain correction, the captured image becomes the same as the image before the gain correction with respect to the gain of each pixel 100.

  In the next step S210, the positions of the cinch step component and the glass step component are detected from the captured image obtained in step S208. The detection method of the position of the cinch step component and the glass step component is not particularly limited. As a specific example, the control unit 30 according to the present embodiment detects a cinch step and a glass step by detecting a straight line (an image representing a straight line) from the captured image, and based on the detected cinch step and the glass step. , Position of cinch step component and glass step component are detected. The method of detecting the straight line is not particularly limited, and a general method may be used, for example, Hough transform (Hough transform) or the like may be used.

  In addition, when detecting a straight line from the photographed image, a process of detecting the straight line may be performed on the entire photographed image, but the positions of the cinch step and the glass step are estimated and the area including the estimated position is included. It is preferable to perform processing for detecting a straight line. For example, it is possible to obtain a range in which the position of the cinch step component and the position of the glass step component can be obtained by design or experiment or the like, and to estimate that the cinch step and the glass step are within the range. Also, for example, the positional shift amounts of the cinch step component and the glass step component are obtained based on design or experiment, etc., and based on the cinch step and the glass step and the positional shift amount previously detected from the gain calibration image. It may be inferred that there is a cinch step and a glass step within the range. As described above, the process of detecting the straight line in the area including the estimated position can improve the detection accuracy as compared to the process of detecting the straight line in the entire captured image.

  In addition, since the difference in the transmittance of the radiation X is smaller than that of the cinch difference, the difference in concentration between the glass difference component and the ordinary component is small. Therefore, the cinch step component (cinch step) may be detected first, and then the position of the glass step component may be detected based on the detected cinch step position.

  In the next step S212, the position of the step component of the gain calibration image is corrected to be matched with the position of the step component of the photographed image detected in step S210 by converting the coordinates of the gain calibration image after defect correction. In the present embodiment, the coordinate of the image is the coordinate (position) of the pixel, and the y direction is the long direction (sub direction) along which the radiation irradiating apparatus 16 moves, and the x direction intersects the long direction. Direction (main direction). The conversion method of the coordinates is not limited, and examples thereof include a method of translating the step component of the gain calibration image, a method of rotating, and a method of deforming the shape of the step component. As a specific example of the method of deforming the shape of the step component, the step component of the gain calibration image is deformed into a parallelogram in the auxiliary direction according to the angular deviation between the detected step of the gain calibration image and the step of the photographed image. Can be mentioned (see FIG. 10). When the parallelogram shape is deformed in this way, it is not necessary to consider the image information of the area that is out of the rectangle when applied to the rectangular gain calibration image.

In the Geinkyaribu image shown in FIG. 10 shows a step component caused by the radiation image capturing apparatus 14 _1, in fact, it has also caused the stepped component by radiographic imaging device 14 _3. Therefore, the control unit 30 converts the coordinates of both step components of the gain calibration image to correct the position of the step component. When the step component is generated at only one of the ends of the captured image, the coordinates of the entire captured image may be converted to correct the position of the step component.

  In order to generate a gain correction image for gain correction, it is preferable to perform processing in which an image (corresponding to a normal component) between both step components subjected to coordinate conversion is smoothly connected to each step component.

  In the next step S214, the control unit 30 performs gain correction on the photographed image on which the inverse gain correction has been performed in step S208, based on the gain calibration image whose position of the step component has been corrected by the process of step S212.

  In the gain correction in this step, since the position of the step component of the gain calibration image is aligned with the position of the step component of the photographed image, the number of steps does not become four as in the gain correction performed in step S206. Gain correction can be appropriately performed.

  Furthermore, in the console 20 of the present embodiment, correction (step correction) of the step component generated in the captured image is performed. In the present embodiment, the step correction refers to a correction for reducing the difference in density between the density of the step component and the density of the normal component. By performing the offset correction, the gain correction, and the defective pixel correction in advance, the step correction can be appropriately performed.

  Therefore, in the next step S216, first, the control unit 30 performs level difference correction of the glass level difference component. A specific example of step correction of the glass step component performed by the control unit 30 according to the present embodiment will be described. Since the step is generally not horizontal (y coordinate is constant) but oblique, in the x range in which the y coordinate is constant, for example, referring to the technique described in Japanese Patent Laid-Open No. 2009-285354. Make corrections. Since vertical stripes occur at the x range boundary where the y coordinate changes, the corrected image (computed by smoothing the difference between the pixel values of the adjacent y coordinate of the boundary in the main direction) is smoothed in the x direction. Occurrence of streaks can be prevented.

  In addition, the method of the level difference correction of the glass level difference component is not limited to a specific example of the present embodiment, as long as the concentration difference between the concentration of the glass level difference component and the concentration of the normal component can be reduced. Good.

  In the next step S218, the control unit 30 performs step correction of the cinch step component. A specific example of the step correction of the cinch step component performed by the control unit 30 of the present embodiment will be described. The control unit 30 according to the present embodiment performs step correction by dividing the cinch step component into two regions.

On the photographed image, for areas where the image information to the captured image of the upper of the radiographic image capturing apparatus 14 ₍₁₄ 1, 14 ₃₎ are present (overlapping region), the upper radiographic imaging device 14 ₍₁₄ 1, 14 ₃ The image information of) is diverted. Therefore, in the present embodiment, correction is performed on the captured image of the upper radiation imaging device 14 (14 ₁ , 14 ₃ ) _first . For the coordinates (address) of the area (overlap area) of the image information to be diverted, a setting value or a value obtained by experiment or the like is obtained in advance, and the storage unit 50 of the console 20, in each radiation imaging device 14, and It may be stored in a control unit or storage unit (not shown) in the electronic cassette 12 or the like.

Further, as shown in FIG. 5A, the upper radiographic imaging device 14 ₍₁₄ 1, 14 _3), than the lower of the radiographic image capturing apparatus 14 (14 _2), because the SID is different, the upper diverting It is preferable to match the enlargement ratio of the photographed image with the lower photographed image. As with the area of the image information to be diverted, the enlargement ratio is obtained in advance as a set value or a value obtained by experiment or the like, and the storage unit 50 of the console 20, the inside of each radiation imaging device 14, and the inside of the electronic cassette 12 It may be stored in the control unit or storage unit (not shown) or the like.

  In addition, in the region other than the overlap region, the correction amount is calculated so as to connect the overlap region and the cinch step smoothly, and the calculated correction amount is subtracted.

  In this way, when the step correction of the cinch step component generated in the captured image is completed, the control unit 30 ends the main image processing. The photographed image after the main processing (after the level difference correction) is stored in the storage unit 50.

  In addition, the part which was a level | step difference component may be an image with discomfort with respect to a normal component part. For example, the graininess of the image may be different between the portion that was the step component and the normal component portion. Therefore, it is preferable to perform various processes for further improving the image quality on the photographed image after the main process.

  The control unit 30 causes the display unit 34 of the console 20 to display the captured image of each of the radiation image capturing devices 14 corrected in this manner, outputs the image to be displayed on a reading device (not shown), and outputs it to the PACS 22 Do. Note that the control unit 30 may connect the photographed images (after correction) by the respective radiation image photographing devices 14 and display or output them as a single radiation image, or may individually display or output them. .

As described above, the electronic cassette 12 of the present embodiment includes the three radiographic imaging devices 14 (14 _{1 to} 14 ₃ ). Radiographic imaging apparatus 14 _1, 14 ₃ are the upper side (the side close to the radiation irradiation device 16), the radiation image capturing apparatus 14 ₂ is arranged in a so-called terrace shape having a (the side far from the radiation irradiation device 16) lower.

  The control unit 30 of the console 20 acquires in advance the gain calibration image of each of the radiographic imaging devices 14 captured by the radiation X emitted from the position A, and stores the acquired gain calibration image in the storage unit 50. When imaging of the subject 18 is performed, the control unit 30 acquires a captured image from each of the radiation image capturing devices 14 and temporarily stores the captured image in the storage unit 50.

The control unit 30 performs gain correction of the captured image of the upper radiation image capturing apparatus 14 (14 ₁ , 14 ₃ ) based on the gain calibration image stored in the storage unit 50.

On the other hand, the captured image of the lower radiation imaging device 14 (14 ₂ ) is caused by the step of the end of the scintillator 98 and the TFT glass substrate 90 of the upper radiation imaging device 14 (14 ₁ , 14 ₃ ) Step components (cinch component and glass component) are generated. The control unit 30 detects the positions of the cinch step component and the glass step component from the photographed image and the gain calibration image. The control unit 30 corrects the positions of the cinch step component and the glass step component by converting the coordinates of the cinch step component and the glass step component of the gain calibration image in accordance with the positions of the cinch step component and the glass step component of the photographed image. Do. The control unit 30 performs gain correction of the photographed image based on the corrected gain calibration image.

  In the present embodiment, the positions of the cinch step component and the glass step component change according to the position (the incident angle of the radiation) of the radiation irradiating device 16 and the movement (movement) of the radiation image capturing device 14. The positions of the cinch step and the glass step substantially move in parallel in the longitudinal direction according to the position (the incident angle of the radiation) of the radiation irradiating device 16. Further, in accordance with the movement (movement) of the radiation imaging device 14, the angles of the cinch step and the glass step change. Therefore, the positions of the cinch step component and the glass step component may be different between the gain calibration image and the photographed image. When the gain correction of the photographed image is performed by the gain calibration image in which the positions of the step components are different, four steps are generated in the photographed image after the gain correction due to the step components of the both.

  On the other hand, the control unit 30 of the present embodiment corrects the positions of the cinch step component and the glass step component of the gain calibration image in accordance with the positions of the cinch step component and the glass step component of the photographed image. Since the gain correction of the captured image is performed based on the corrected gain calibration image, the gain correction of the captured image can be appropriately performed. Furthermore, since the step component can be appropriately detected from the photographed image, the step correction of the cinch step component and the glass step component can be appropriately performed.

  Therefore, in the radiation image capturing system 10 (console 20) of the present embodiment, even if the radiation incident direction changes between the gain calibration image and the captured image, correction of the step component generated in the captured image is appropriate. Can be done.

  If the positions of the cinch step component and the glass step component of the gain calibration image detected in advance coincide with the positions of the cinch step component and the glass step component of the captured image detected in step S210, step S212 is performed. The process may be omitted. As described above, when the positions of the cinch step component and the glass step component of the gain calibration image and the photographed image coincide with each other, even if gain correction of the photographed image is performed based on the gain calibration image, four steps are generated as described above. I have not. Therefore, it is possible to appropriately correct the gain of the photographed image based on the gain calibration image.

  Further, in the present embodiment, since the end of the scintillator 98 and the end of the TFT glass substrate 90 are different, a case where steps are generated (two steps are generated) due to each is described. Is determined by the structure of the radiation detector 26 and the like, and is not limited to the present embodiment. It goes without saying that the present invention is applicable regardless of the number of steps.

  Further, the position (irradiation position of the radiation X) of the radiation irradiation device 16 differs between the time of photographing of the image for correction and the time of photographing of the photographed image, not only for the gain calibration image but also for other correction images. It goes without saying that the present invention is applicable to the case.

  Further, the gain correction in step S206 and the inverse gain correction in step S208 may be omitted, and only the defect correction may be performed. By performing steps S206 and S208 as in the present embodiment, the positions of the cinch step component and the glass step component can be detected more appropriately in step S210.

  Further, in the present embodiment, as a method of correcting the positional deviation of the step component, the position of the step component of the gain calibration image is matched with the position of the step component of the photographed image by converting the coordinates of the gain calibration image. Although the correction is made, the correction method is not limited. For example, instead of the gain calibration image, the coordinates of the captured image may be converted. Further, the coordinates of both the gain calibration image and the photographed image may be converted. When the coordinates of the photographed image are converted, the coordinates may be returned to the original (inverse conversion) after gain correction of the photographed image.

  Moreover, although the case where the electronic cassette 12 is provided with three radiation imaging devices 14 has been described in the present embodiment, the number of radiation imaging devices 14 is not particularly limited. Further, the method of overlapping the radiation image capturing apparatus 14 is not limited to the electronic cassette 12 (see FIG. 5) of the present embodiment.

Further, in the present embodiment, the case where a plurality of radiation imaging devices 14 (14 _{1 to} 14 ₃ ) are provided in the housing 13 of one electronic cassette 12 has been described, but a plurality of electronic cassettes are provided. The present invention may be applied to a radiation imaging system. For example, by arranging a plurality of electronic cassettes provided with one radiation imaging apparatus adjacent to each other, a long imaging area may be provided. A specific configuration example in the case where a plurality of electronic cassettes are arranged adjacent to each other is shown in FIGS. In Figure 11 and 12 shows a case disposed adjacent the three electronic cassette 62 ₍₆₂ 1 to 62 _3). Further, FIG. 11 shows a case where the electronic cassette 12 is arranged in a terrace shape, similarly to the radiation imaging device 14 of the electronic cassette 12 of the present embodiment. FIG. 12 shows the case where the electronic cassettes 12 are arranged stepwise.

  Moreover, although the case where this invention was applied to the radiation detector 26 of the indirect conversion system which converts converted light into electric charge was demonstrated in said each embodiment, it is not limited to this. For example, the present invention may be applied to a direct conversion type radiation detector using a material such as amorphous selenium which directly converts radiation into charge as a photoelectric conversion layer which absorbs radiation and converts the charge into charge.

  In addition, the configurations, operations, and the like of the radiation imaging system 10, the electronic cassette 12, the radiation imaging device 14, the console 20, and the like described in the present embodiment are an example, and the situation does not deviate from the scope of the present invention. Needless to say, it can be changed according to

  Further, in the present embodiment, the radiation of the present invention is not particularly limited, and X-rays, γ-rays and the like can be applied.

10 the radiographic image capturing system 12, 62 the electronic cassette 14, 14 ₁ to 14 ₃ radiographic imaging apparatus 16 radiation irradiation device 18 subject 20 console 26 radiation detector 30 control unit 50 storage unit 90 TFT glass substrate 98 scintillator 100 pixels

Claims (8)

A first conversion layer for converting radiation incident from a radiation irradiation device into light, and a first substrate on which a plurality of first pixels for storing charges generated according to the light converted by the first conversion layer are formed And a first radiation imaging apparatus for taking a first radiation image,
A second conversion layer disposed on a side farther from the radiation irradiating apparatus than the first radiation image capturing apparatus in a state in which a part of the radiation is superimposed on the incident direction and converting the radiation into light; A second radiation image capturing apparatus for capturing a second radiation image, comprising: a second substrate on which a plurality of second pixels for storing charges generated according to the light converted by the second conversion layer are formed;
The conversion layer step indicated by the conversion layer step component obtained by acquiring the first radiation image and the second radiation image and causing the second radiation image to be caused by the first conversion layer of the first radiation image capturing apparatus And a correction unit configured to perform correction to reduce each of the substrate steps represented by the substrate step component generated due to the first substrate of the first radiation image capturing apparatus by a different correction method,
Radiographic imaging system equipped with The correction unit performs correction to reduce the conversion layer step by the first radiation image.
The radiation imaging system according to claim 1. The correction unit diverts an image of a region corresponding to the overlap region of the first radiation image, regarding an overlap region in which image information is present in the first radiation image among the conversion layer step components. Make corrections,
The radiographic imaging system of Claim 1 or Claim 2. The correction unit derives and derives a correction amount for smoothly connecting the first radiation image and the conversion layer step diverted to each other in the area different from the overlap area among the conversion layer step components. Perform correction by the correction amount,
The radiation imaging system according to claim 3. The correction unit corrects the conversion layer step after correcting the substrate step.
The radiation imaging system according to any one of claims 1 to 4. A first conversion layer for converting radiation incident from a radiation irradiation device into light, and a first substrate on which a plurality of first pixels for storing charges generated according to the light converted by the first conversion layer are formed And a part of the first radiation image captured by the first radiation image capturing apparatus, and a part of the first radiation image captured in the incident direction of the radiation on the side farther from the radiation irradiating device than the first radiation image capturing apparatus A second conversion layer for converting the radiation into light, and a plurality of second pixels for storing charges generated according to the light converted by the second conversion layer. And acquiring a second radiation image captured by a second radiation imaging device including a substrate, and generating the second radiation image due to the first conversion layer of the first radiation imaging device. Indicated by conversion layer step component An image processing apparatus comprising: a correction unit that performs correction to reduce each of a conversion layer step and a substrate step represented by a substrate step component generated due to the first substrate of the first radiation image capturing device by a different correction method . A first conversion layer for converting radiation incident from a radiation irradiation device into light, and a first substrate on which a plurality of first pixels for storing charges generated according to the light converted by the first conversion layer are formed A first radiation image capturing apparatus for capturing a first radiation image, and a part of the first radiation image capturing apparatus superimposed on the radiation incident direction on a side farther from the radiation irradiation apparatus than the first radiation image capturing apparatus; A second conversion layer disposed in a fixed state, the second conversion layer converting the radiation into light, and a plurality of second pixels forming a plurality of second pixels storing charges generated according to the light converted by the second conversion layer And a second radiation image capturing apparatus for capturing a second radiation image, the control method of a radiation image capturing system comprising:
Acquiring the first radiation image and the second radiation image;
A conversion layer step indicated by a conversion layer step component generated due to the first conversion layer of the first radiation image capturing device with respect to the second radiation image, and the first substrate of the first radiation image capturing device Performing correction to reduce each of the substrate steps represented by the substrate step component caused by
Control method of a radiographic imaging system provided with   A control program of a radiation imaging system for causing a computer to execute each step of the control method of the radiation imaging system according to claim 7.